Posse Comitatus Act Limits Armed Services at Home

For 125 years, it's been the law of the land, and it's served this nation well. And the Bush Adminstration wants it weakened or overturned. Will "libertarians" please explain to me why the Republicans are the lesser evil? (Not that I think that the Democrats are evil, but the "libertarians" do.) Or are armed soldiers patrolling the streets part of the libertarian vision?