Arguments before the U.S. Supreme Court this week concerning gay marriage and the constitutionality of the federal Defense of Marriage Act represent just one example of a growing list of clashes that are pitting the federal government against states' rights.

The court this week considered a California law that bans gay marriage. It also considered a lawsuit that says the federal Defense of Marriage Act discriminates against same-sex couples who are legally married but who cannot take advantage of federal benefits now afforded to heterosexual married couples.

DOMA by its very nature is discriminatory. Either the law should be struck down or the federal benefits that heterosexual married couples enjoy should be eliminated. Couples who comply with state laws, regardless of their sexual orientation, should have an expectation that all who follow the law should be treated equally.

Maryland legalized gay marriage, and the law withstood a petition challenge that put the measure before voters. Gay couples are now on equal footing with heterosexual couples at the state level, but they remain discriminated against at the federal level.

The state legislature this year is also considering a bill to decriminalize marijuana. Other states that have done so, or that have enacted medical marijuana laws, are also finding themselves in a fight with the federal government.

In January, The New York Times reported on a family man and entrepreneur who followed all of California's laws in setting up a marijuana-growing operation. That didn't stop the federal Justice Department from leveling charges against Matthew Davies. The prosecution is coming despite President Barack Obama's statement that the Justice Department would not pursue this type of prosecutions, and that it had "bigger fish to fry."

Colorado, which just passed a law decriminalizing marijuana, is wrestling with similar federal concerns, as are other states that have legalized or decriminalized marijuana.

The federal government has always tried to expand its control over states. In some cases, federal-level intervention was necessary to correct systematic problems. In other cases, states have seen such acts as merely attempts to usurp their authority.

States' rights are an essential part of our governing system. The federal government should only intervene in cases where discriminatory policies exist or problems arise that impact people outside the specific state's laws.

Regardless of the court's ruling in the gay marriage cases, look for more battles between states and the federal government in the coming years on everything from legal marijuana to environmental issues.