Ilya Somin of the Cato Institute has a report on Supreme Court nominee Samuel Alito noting that he has a decidedly libertarian streak in many of his rulings. Somin writes:
Most debate about Supreme Court nominee Samuel Alito has focused on his propensity to vote to overrule Roe v. Wade and the similarity between him and conservative Justice Antonin Scalia. But despite the superficial parallels between the two conservative, Italian-American Catholic jurists, it is important to recognize that Alito has a substantial libertarian dimension to his jurisprudence as well as a conservative one. In several key fields of law, he is more likely than Scalia and other conservatives to be skeptical of assertions of government power. More important, there is much in his record that should appeal to libertarians and -- to a lesser extent -- even left-wing liberals.
In most judicial cases, the correct result is sufficiently clear that differences in judicial philosophy are unlikely to affect the outcome. However, they often do matter in cases where the issue at stake is controversial, and traditional legal materials do not strongly favor one side or the other. While judges should not simply vote for whatever outcomes because they prefer them on policy grounds, a libertarian orientation helps sensitize jurists to the fact that the Constitution is meant to constrain government, not just empower electoral majorities, as some conservatives claim. Here Alito's libertarian streak and his differences with Scalia may have an impact.
In sharp contrast to Scalia, Alito has often voted in favor of the free exercise rights of minority religious groups, even against laws that are not deliberately intended to harm minority religions. In Fraternal Order of Police v. City of Newark (1999), he joined an opinion holding that Muslim police officers had a right to grow beards (as required by their religion) so long as the city allowed a secular health-related exemption from its no-beard policy. This result is in tension with Scalia's position in the important case of Employment Division v. Smith, where he wrote a decision holding that the Constitution in most cases does not protect religious groups against the effects of "neutral" laws. Given that the FOP case involved Muslims, it is hard to argue that Alito was just voting for the rights of a group whose religious values he shares. In another case, Blackhawk v. Pennsylvania, Alito authored an opinion establishing a free exercise exemption for a Native American religious group. While these Alito decisions do not directly contradict Smith, they certainly provide much stronger protections for minority religious groups than Scalia would be likely to favor.
Alito also differs from Scalia on the key issue of federalism. In United States v. Rybar (1996), Alito dissented from a case upholding a federal statute banning machine gun possession. Alito argued that a categorical ban on the intrastate ownership of machine guns falls outside of Congress's power to regulate interstate commerce. The case cannot be explained, as some might believe, on the grounds that Alito somehow sympathizes with private ownership of machine guns. In the opinion, he favorably refers to state bans on machine gun possession. Alito's position differs from Scalia's recent opinion in Gonzales v. Raich, where the Justice argued that the commerce power justified upholding a federal ban on the possession of marijuana, even for noncommercial medical purposes permitted under state law.
There's more detail in the link above.
I fail to see how ruling in favour of free exercise marks him out as being particularly libertarian. Fair enough it distinguishes him from Scalia, but even principled social conservatives can see that free exercise is a fully fledged enumerated right. The smarter ones even recognise that protecting minority rights is the best way to protect majority rights, in the long term. The problem is with Scalia's lack of principle. Similarly federalism isn't necessarily a mark of libertarianism - if a state regulates something rather than the feds it's still regulated.
I fail to see how a libertarian could uphold a law that intrudes into the marital relationship. I have no problem with a libertarian being pro-life, but forcing a wife to tell her husband about plans to undertake a legal medical procedure??
Not to mention, aren't libertarians more inclined (if not by definition) take an expansive view of the 9th Amendment? No one who says "The Constitution nowhere grants a right to blank" can be considered libertarian.