LOS ANGELES — The approval of fresh sanctions on Iran marks the third time that the United Nations Security Council has been galvanized to stem the Islamic Republic's feared uranium enrichment efforts. Unfortunately, the new sanctions are unlikely to be any more effective than the first two rounds.

Consider the two earlier Security Council resolutions. The December 2006 resolution curbed international assistance to Iran in mastering the nuclear fuel cycle. The March 2007 resolution called for "vigilance and restraint" in the sale of heavy weapons to Iran and avoidance of new grants, financial assistance or concessional loans. Neither moved the country's ruling mullahs. Few expect a different outcome from the new sanctions, which authorize international interception of Iranian contraband and tightened monitoring of the regime's financial institutions, along with travel limitations and asset freezes applied to people and companies involved in Iran's nuclear program.

The failure of targeted U.N. sanctions should come as no surprise. The U.S. has been on the sanctions treadmill for years. Between 2003 and 2007 the U.S. Treasury Department brought litigation against 94 companies for violating the ban against trade and investment in Iran. The State Department imposed sanctions 111 times against foreign entities that engaged in proliferation or terrorism-related activities with Iran. And both departments have used their power to freeze financial assets or access to the U.S. financial system.