A push by the shipping industry to roll back state protections against contaminated ballast water discharges has been denied in federal court.

The industry opposed a decision by the U.S. Environmental Protection Agency to allow individual states to set stricter standards for their own waters than those issued by the federal government. The issue is critical to Great Lakes states, many of which - including Wisconsin - have set ballast water standards stricter than those being developed by the EPA under the Clean Water Act.

In a ruling issued Friday, the U.S. Court of Appeals for the District of Columbia ruled the EPA can allow states to set their own standards.

Conservation groups called last week's ruling a victory for a system of lakes that has been ravaged by invasive species outbreaks spawned by contaminated ballast discharges.

"The court got it right," said Thom Cmar, an attorney with Natural Resources Defense Council, which intervened in the case on behalf of the EPA. "In absence of a strong national standard, these state standards are necessary to fill the void that's been created by a failure of federal leadership on the issue."

Congress has been considering its own single, overarching ballast water standard for ship discharges for years but has yet to act.

The American Waterways Operators, which asked the court to block the EPA from allowing individual state standards, said Friday's ruling underscores the need for new national ballast law so vessel operators have to meet only a single standard, not the patchwork that is emerging based on individual states' rules.

"In light of the Court's ruling, AWO encourages Congress to move quickly to eliminate the current confusing and contradictory patchwork of requirements and establish an improved regulatory regime for vessel discharges that ensures both environmental protection and economic growth," American Waterways Operators said in a news release.

The ruling comes at a time when a 2012 appropriations bill moving through the U.S. House would block states from receiving EPA funds if they adopt ballast rules that are more stringent that those of the agency, something conservation groups are vigorously criticizing.