Undeniably, California’s dominant Democratic Party is joined at the hip with labor unions, even though scarcely a sixth of the state’s workers belong to unions.

Unsurprisingly, therefore, Democratic politicians push laws and regulations to help unions expand their memberships.

They are motivated, they say, by their belief that workers’ lives are improved by union representation. It’s also true, however, that unions are the largest single source of their campaign funds and other support.

Whatever the motives, there’s a steady flow of union-backed laws from Sacramento, such as efforts to expand the state’s “prevailing wage” law, originally limited to public works projects, to private construction, or making home care workers public employees so they could be unionized.

How far, one might wonder, can Democrats go to help their union friends? Pretty far, the state Supreme Court seemed to say last week in validating a special law passed 15 years ago to boost the struggling United Farm Workers Union.

The law empowers the Agricultural Labor Relations Board to impose contracts when the UFW and an agricultural employer reach an impasse.

The court case arose out of a decades-long dispute involving the UFW and Gerawan Farming, one of the state’s largest agricultural operations.

The UFW won a representation election in 1990, but never negotiated a contract. Decades later, the union tried to negotiate a contract based on the election, but Gerawan claimed that it had abandoned its right to negotiate, touching off years of wrangling.

The ALRB essentially sided with the union, but Garawan took the issue to court and eventually won when a state appellate court declared that the law “violates equal protection principles.”

Unanimously, the Supreme Court overturned that ruling and declared that Gerawan could not ignore the 1990 election’s outcome on grounds that the UFW had abandoned negotiations.

Gerawan says it will appeal to the U.S. Supreme Court, but if the state ruling stands, it will not only be a major victory for the UFW but encourage other unions to ask a friendly Legislature for similar boosts.

The next test of limits, if any, on pro-union legislation may involve electric car maker Tesla.

Tesla has been involved in a duel with the United Auto Workers Union over efforts to organize thousands of Tesla workers. The union says the workers are being mistreated and filed a complaint with the National Labor Relations Board.

Tesla and its famous founder, Elon Musk, have denied the allegations and contend that workers are treated and compensated fairly.

In September, during the dying moments of the 2017 legislative session, Gov. Jerry Brown and legislators reached agreement on how to spend $1.5 billion in proceeds from auctions of greenhouse gas emission permits.

One of the appropriations would beef up the state’s rebates to purchasers of zero-emission vehicles, like Tesla. But at the last moment, language was inserted to require a company whose customers get rebates to be certified by the Air Resources Board and the state labor commissioner “as being fair and responsible in the treatment of their workers.”

It’s clearly aimed at Tesla at a critical moment in its brief history. It’s counting on sales of a new, lower-priced model to move into the mass market and become profitable, it needs rebates to entice customers, and it faces a potential loss of federal rebates.

Implicitly, politicians are telling Tesla to either cooperate with the UAW or be frozen out of rebates, which would still flow to customers of Tesla rivals.

The situation has a tinge of irony. Brown and the legislators who enacted the law, such as Senate President Pro Tem Kevin de León, have been claiming that California has cut climate change emissions while building a “green” economy and holding up Tesla as a prime example.