The Trump administration is pursuing ways to protect domestic vehicle manufacturing by forcing imported cars to meet stricter environmental rules when entering the country, according to senior administration and industry officials, a move that would make imports more expensive.

The cost of meeting the stiffer import standards would, at least in part, be passed along to U.S. consumers. This style of “nontariff barrier”—a protectionist stratagem the U.S. has long condemned in other countries—is designed to reduce the relative cost of cars manufactured in the U.S., by American workers, the officials said.

President Donald Trump has asked the Environmental Protection Agency and several other agencies, including the Commerce and Transportation departments, to pursue plans to use such laws as the Clean Air Act to subject cars made overseas to strict emissions-standards testing and reviews when entering the U.S. The rules could effectively require more expensive technology on some foreign cars or subject those cars to more expensive hurdles that can be billed to the manufacturer or importer.

Either option would likely raise the costs for foreign cars sold in the U.S., making domestically produced cars cheaper by comparison. This effect of raising prices on consumers is common to most nontariff barriers, which seek to penalize imports through measures other than tariffs or duties.

The initiative remains in the planning stages and still faces hurdles to implementation. EPA officials are working now to craft a legal justification that would meet a high requirement of legal rationale, given any proposal is expected to draw lawsuits. Some in the administration see the idea as too radical, and the considerable legal challenges have already delayed the plan.