Gun owners in California recently woke up to the news that the California Senate had passed a stack of bills putting new restrictions on the use of guns.

If they all become law, you’ll need a license to sell ammunition and a background check to buy it, magazines that hold more than 10 rounds will be illegal, more guns will be classified as “assault weapons,” homemade guns will need state serial numbers, and it will be a crime to loan a gun to anyone who isn’t a family member or a licensed hunter.

Are those proposed laws constitutional?

The Supreme Court said in 2008, in District of Columbia v. Heller, that Americans have the right as individuals to keep and bear arms. The court struck down Washington, D.C.’s, “absolute prohibition of handguns held and used for self-defense in the home.”

But the Heller decision left many questions unanswered, starting with whether the Second Amendment was binding on the 50 states as well as on the District of Columbia.

When the first 10 amendments to the Constitution were ratified in 1791, nobody thought they applied to the states. Chief Justice John Marshall wrote in 1833 that if Congress had intended the Bill of Rights to bind the states, “they would have declared this purpose in plain and intelligible language.”

That understanding still prevailed at the start of the 20th century, as bank robber “Gunplay” Maxwell discovered. In 1900 he complained that Utah had denied his Sixth Amendment right to trial by jury, but the U.S. Supreme Court said the first 10 amendments “were not intended to and did not have any effect upon the powers of the respective states,” adding, “This has been many times decided.”

The Supreme Court never said the whole Bill of Rights applies to the states. Instead, there was a gradual process of selectively declaring particular rights to be “fundamental” to liberty. That makes them apply to the states through the Fourteenth Amendment, which says the states can’t deny liberty to any person without due process of law.

“Gunplay” Maxwell was ahead of his time. The Supreme Court decided that trial by jury was “fundamental” to liberty in 1968.

In 2010, two years after the Heller decision, the right to keep and bear arms was declared “fundamental” in McDonald v. Chicago.

This gradual “incorporation” of the Bill of Rights into the Fourteenth Amendment has been going on for about 90 years and has silently transferred power from state legislatures to federal courts. For example, in 2011 the Supreme Court struck down a California law that banned the sale of violent video games to minors. The justices said California had not shown the court a “compelling” reason to have a law that infringes the First Amendment rights of video game creators.

Soon, California may have to show the court a “compelling” reason for laws that infringe the Second Amendment rights of gun owners.

For 90 years, the justices have invented balancing tests and “scrutiny” levels to guide decisions in these cases, but it remains what Justice Felix Frankfurter called it in 1947: “merely subjective.”

Does California have a “compelling” reason to require background checks for ammunition purchases? One justice may think so, but another may find the reason “only rational.” Five votes for “compelling” would uphold such a law, while five “only rationals” would be enough to strike it down.

Over the next decade, Second Amendment rights will be profoundly affected by the personal values of the justices appointed by the president who’s elected this November.

The NRA made an early endorsement and started the fight before June.