How to explain America’s failure, after 20 years of efforts, to impose genuinely crippling sanctions on Iran? Start with the penchant of the executive branch—from Presidents Clinton to Obama—for excluding Congress from the process.

Last month, the New York Times reported that President Obama planned to bypass Congress on any final deal with Iran, directly violating a pledge by Secretary of State John Kerry earlier this year that the administration would “of course” consult with lawmakers about the future of sanctions. “We’d be obligated to,” he said, “under the law.”