The Wall Street Journal describes Egyptian President Mohammad Morsi's power grab as an "Islamist Coup."

Mr. Morsi says his diktat will merely last as long as it takes the country to adopt a new constitution, which is what authoritarians always say. They claim to be a necessary step on the way to democracy, but democracy never arrives. Mr. Morsi's rationalization is that he must have this power to "protect the revolution," as if the demonstrators who deposed Hosni Mubarak in 2011 merely wanted another Mubarak with a beard and prayer rug. Mr. Morsi is claiming more power than Mr. Mubarak ever had.

Egyptians took to the street on Friday in protest, sometimes violently, and nearly every other major political leader denounced the putsch. That includes Abdel Monheim Aboul Fotouh, a former Muslim Brotherhood leader and presidential candidate. The violence is regrettable, but the protests may be the only way Egyptians can prevent the Muslim Brotherhood from becoming their new dictators.

The Brotherhood doesn't control the military or Ministry of Interior, yet neither one is going to rush to defend a more liberal Egyptian state. The military's main goal is to protect its role in government and its economic interests, and the Brotherhood's draft constitution puts the military outside of civilian control.

As long as Mr. Morsi doesn't challenge those interests, the military and police may let him control the courts, the media and the legislature. This is a recipe for rule a la Pakistan, with an increasingly Islamist state but the military and intelligence services as an independent power. The immediate losers will be Egypt's liberals and the Western journalists who inhaled the vapors of Tahrir Square. But whatever Mr. Morsi intends, the Pakistan model is not a recipe for a more stable Egypt.

Mr. Morsi's coup is also awkward for the Obama Administration, which had been praising the Egyptian in media backgrounders for his role in brokering the cease-fire between Israel and Hamas. Mr. Morsi was hailed as a moderate statesman. Yet Secretary of State Hillary Clinton had barely left Cairo before Mr. Morsi made his move. He may have figured that all the praise made it easier for him to grab more power.

US support has enabled Morsi's power grabs since he took office. As long as there were no consequences for sacking generals who weren't Islamists, taking power from the legislature, and instituting Sharia law, Morsi could act with impunity.

But this move to put himself above the judiciary is different and if Obama won't punish Egypt for Morsi's rise to the dictatorship, then the US congress should. A move to withhold aid could rouse the Egyptian military who could force him to back down. That's about all that the Egyptians have left to stop the Muslim Brotherhood from a complete takeover of the country.