Why Is Retroactive Immunity Necessary to Assure Future Cooperation?

It looks like the Senate (but not, so far, the House) is prepared to grant retroactive legal immunity to telecommunications companies that violated the Foreign Intelligence Surveillance Act by allowing warrantless monitoring of international phone calls and email involving people in the U.S. Congress approved such surveillance last summer, giving the attorney general and the national intelligence director the power to order it without court approval. That temporary measure, which expires in February, gave telecommunications carriers prospective immunity for cooperating with such surveillance in the future. But the Bush administration says they should also get a free pass for going along with the surveillance when it was still clearly illegal. Whatever the merits of warrantless surveillance aimed at preventing terrorist attacks, why send a message that private companies can break the law with impunity in the name of national security? We want them to worry that cooperating with government agents when such cooperation is illegal could expose them to penalties and lawsuits. We want them to consult their lawyers and think twice. Why bother imposing separate legal obligations on them if the assurances of a goverment agent are enough to make everything OK?