Here's one fairly representative example from the site of Chris Dyer, GOP candidate in Nevada's First Congressional District:
I believe that all human life is sacred. I believe matters regarding abortion, homicide, the death penalty and euthanasia should be handled by the voters of the states, not the federal government.
Let's add in a Libertarian for balance, Michael Benoit in California's 52nd Congressional District:
I can not find in the Constitution where the federal government has any authority in this area, and therefore conclude that it should be left to the states.
Please note: this is not a post about abortion. Truth in advertising: I unequivocally support abortion rights for women. I know that other Libertarians don't. This is a post about the use of States' Rights as an argument or blind by Libertarian candidates.
There are two issues to consider here. The first is the Constitutionalist argument that the 9th and 10th Amendments really should mean something, and that any reversion of right from the Federal government to the State governments moves power and authority closer to the people--which is a good thing. There is a certain merit in this position, but--strictly speaking--it's not a Libertarian position at all. Whether the State happens to be the State or the Federal government, or even your town council, if that entity is exercising aggressive power it is something that Libertarians should oppose.
It is also arguable that the state governments are, in many cases, potentially more oppressive and given to undue influence by special interest groups. In Delaware, for example, we actually have a proposed Constitutional amendment (proposed by one Democrat and one Republican--therefore bi-partisan)--to outlaw not only gay marriage but also civil unions. Thanks to heavy union influence we have a prevailing wage law for state construction that diverts millions of dollars each year from school construction alone. And because our corporations buy and sell local politicians for trivial amounts of money by Congressional standards, we have no virtually accountability for chemical plants to pollute groundwater.
Through the years I have come to realize that when most (I won't say all because there are exceptions) politicians want to relegate a sensitive social issue to the States, they really mean something closer to, I oppose this [if it's abortion rights or gay marriage], but I don't want to have to say it outright. Instead, I'm going to say it should be left to the states.
That's what Bob Barr has done on gay marriage, and that's one of the slimiest of his positions.
Because everybody really knows what he personally feels about those disgusting queers getting together with rings to destroy western civilization.
And that, unfortunately, is what a lot of "Ron Paul" Republicans and social conservatives say when they're trying to get votes from Libertarians who ought to hear alarm bells going off in their heads every single time.