Mexican drug cartels are not only setting up marijuana grow operations in U.S. national parks and other public lands but also have infiltrated a number of Indian reservations, the Wall Street Journal reported Nov. 5.

In fact, Mexican drug operations seem to be expanding on Native American lands faster than anywhere else, accounting for half of all marijuana seizures in Washington last year, for example.

Reservations tend to have large transient populations and mixed-blood populations, making it easy for Mexican growers to blend in. “Around here it’s not easy to tell who’s a tribal member and who’s Hispanic,” says Police Chief Keith Hutchenson of Idaho’s Coeur d’Alene Tribe.

Police also tend to be understaffed on Indian lands — the 2,000-square-mile Colville Reservation in Washington is policed by just 19 tribal police officers — and jurisdictional conflicts between Native American and federal and state law-enforcement officials also can end up aiding growers and traffickers.

Some reservations also have become bases for gunrunners smuggling weapons into Mexico as cartels battle with federal forces.

This news summary has been revised to reflect the following correction:

Correction, Nov. 12, 2009: The original summary spelled Colville Reservation incorrectly.