Given sporadic attention for years, the concept of a border fence took on new life after the Sept. 11, 2001, terrorist attacks, which also revived the nation's heated immigration debate. Intelligence officials have said the holes along the southwest border could provide places for terrorists to enter the country.
On Monday, the court declined to hear arguments in a case brought by environmental groups that could have slowed or even halted the multibillion-dollar fence project that stretches from the Pacific surf at Tijuana to the Gulf of Mexico near Brownsville, Texas. Some 331 miles of fencing had been constructed as of June 13, with about as much still to go.
The case involved a two-mile section of fence in the San Pedro Riparian National Conservation Area near Naco, Ariz. The section has already been built. Environmentalists have said the fence puts already endangered species such as two types of wild cats - the ocelot and the jaguarundi - in even more danger. The fence would prevent them from swimming across the Rio Grande to mate.
Fourteen House Democrats - including seven committee chairs - had filed a brief in support of the environmentalists' appeal.
"Without a comprehensive plan, this fence is just another quick fix," said Rep. Bennie Thompson, D-Miss., one of the signers.
Thompson chairs the House Homeland Security Committee.
On the other side, Rep. Peter King, R-N.Y., said the outcome "was a victory for common sense ... and it was a victory for Americans who want secure borders." King wrote the 2006 law that called for hundreds of miles of fencing.
So far, Homeland Security Secretary Michael Chertoff has waived more than 40 laws and regulations in an effort to finish building 670 miles of fence along the southwest border. Administration officials have said that invoking the legal waivers - which Congress authorized in 1996 and 2005 laws - will cut through bureaucratic red tape and sidestep environmental laws that would otherwise stand in the way of construction.
The fence faces other legal challenges. Currently there are two class action lawsuits against property condemnation and four District Court cases challenging environmental actions, according to Homeland Security.
An environmental lawsuit stopped construction of a border fence in San Diego in the late 1990s. Because of this, in 2005 Congress gave the administration wide-reaching power to waive environmental and other laws that could stand in the way.
The fact that the Supreme Court would not take up the Arizona environmental challenge does not mean other lawsuits don't have a chance, said Celestino Gallegos, an attorney with Texas RioGrande Legal Aid. Gallegos' organization has worked with many South Texas landowners who face condemnation. The landowners argue that the government did not properly consult with landowners before filing condemnation lawsuits. The fencing plan affects about 480 landowners.
Defenders of Wildlife attorney Brian Segee said there are "serious constitutional problems" with the law Congress passed in 2005, "which places the unprecedented and extraordinary power with one individual, the secretary of homeland security, to pick and choose which laws apply along the southern border."
Russ Knocke, a spokesman for Homeland Security, said, "As fence construction proceeds, the department will continue to be a good steward of the environment, and consult with appropriate state, local, and tribal officials."
In the second case Monday, the justices, acting at the administration's urging, agreed to review a federal appeals court ruling that limits the use of sonar in naval training exercises.
Sonar, which the Navy uses primarily to locate enemy submarines at sea, can interfere with marine mammals' ability to navigate and communicate.
The administration says the decision by the 9th U.S. Circuit Court of Appeals in San Francisco could cripple the Navy's ability to train sailors and Marines for service in wartime.
The government also says that its use of mid-frequency sonar in training exercises hasn't caused any documented harm to dolphins or been proven to be involved in the beaching of whales - and that national security can trump other interests in some cases anyway.
Some environmentalists said the Supreme Court's hearing of the case could finally settle what takes precedence - national security or environmental protection.
Although the science is inconclusive, there is strong evidence that sonar affects marine mammals. The Navy's environmental assessment of the use of sonar in 14 training exercises off the California coast found it could disturb or harm an estimated 170,000 marine mammals, including causing temporary loss of hearing in at least 8,000 whales.
The case will be heard next fall.
In what is likely to be its final week before a long summer recess, the court has yet to resolve three major outstanding cases - the consideration of Americans' gun rights, whether Exxon Mobil Corp. must pay punitive damages for the Exxon Valdez oil spill in 1989 and the constitutionality of imposing the death penalty on people convicted of raping children.
The court will meet again on Wednesday.
