The government is not allowed to:
5 US Code §552a(e)(7) commands that any Federal agency
“(7) maintain no record describing how any individual exercises rights guaranteed by the First Amendment unless expressly authorized by statute or by the individual about whom the record is maintained or unless pertinent to and within the scope of an authorized law enforcement activity;”
This wouldn’t protect some blogger making viable threats against a politician (and rightly so). But it could be used to punish someone in the Federal Government (and rightly so) for keeping records of your peaceful opposition to proposed legislation (if that link goes dead here is a saved version of the page from Whitehouse.gov as of August 8, 2009 at 2315 PDT).