Senator Sanders called Tuesday for a “sense of urgency” by President Obama to make federal commodity regulators enforce a law against excessive speculation in crude oil markets. In an interview on MSNBC, Sanders cited economists who blame much of the pump price for gasoline on oil speculators. Sanders first staked out his case in a letter to the president last month asking him to intervene with the Commodity Futures Trading Commission. “I urge you to make it clear to the CFTC that they must obey the law and establish strong oil speculation limits as soon as possible. I would also urge you to ask for the immediate resignation of any CFTC commissioner who refuses to obey the law and nominate someone else who will.” Last week, Sanders assembled a group of senators who met with Gary Gensler, the commission chairman, asking him to implement emergency powers to crack down on oil speculators, but he declined. “The president has got to become involved in this issue,” Sanders said.