Police in Fort Bend County are hunting a local man whose abrasively worded pickup sticker has set tongues wagging.

Sheriff Troy E Nehls posted a photo on Facebook of the pickup driving down the FM 395, with a decal reading 'F**k Trump and f**k you for voting for him' on its back window.

'Our Prosecutor has informed us she would accept Disorderly Conduct charges regarding [the sticker], but I feel [police and the driver] could come to an agreement regarding a modification to it,' he wrote.

Trucking hell: This truck has been causing consternation in Texas - and now cops in Fort Bend County want to track down its owner on grounds of 'disorderly conduct'

The photo doesn't show the truck's license plate or any distinguishing features, other than a Mexican skull decal and another sticker about dogs.

Nehls seemed to hope that his post might bear fruit; instead, it bore the brunt of a lot of angry Facebook posters.

Free speech: Sheriff Troy E Nehls (pictured) says he may back off if the sticker is modified - but his threats are undermined by a Supreme Court constitutional ruling

'Your prosecutor should concentrate on real crime,' wrote Antonio Herrera, while Alissa Nguyen said: 'What A Joke. Love Seeing our law enforcement wasting time and energy on pointless s**t.'

And Kasey Rose-Hodge remarked: 'If I had to explain what "grab them by the p***y" meant to my kids, you can explain "F**k Trump" to yours.'

In an attempt to impress upon the commenters the importance of this investigation, Nehls posted the definition of disorderly conduct according to local law.

It cites using 'abusive, indecent, profane, or vulgar language in a public place' that 'tends to incite an immediate breach of the peace'.

However, should the prosecutor attempt to press charges, he or she may find themselves hitting a Supreme Court-shaped brick wall.

In 1971, in the case Cohen v California, the Supreme Court overturned a conviction against a 19-year-old Paul Robert Cohen for wearing a jacket reading 'F**k the draft' in a courthouse.

In a statement, Justice John Marshall Harlan II wrote: 'Absent a more particularized and compelling reason for its actions, the State may not, consistently with the First and Fourteenth Amendments, make the simple public display of this single four-letter expletive a criminal offense.'

He added: 'one man's vulgarity is another's lyric.'

The Texas chapter of the ACLU tweeted Nehls to make that exact point, including a photograph of a book citing the constitutional protection for 'profane and indecent language'.

'You can't prosecute speech just because it has the word "f*ck" in it,' they tweeted, adding: '(And the owner of the truck should feel free to contact @ACLUTx.) #ConstitutionalLaw101 #FreeSpeech'

Court in the act: As pointed out by the ACLU, in 1971 the Supreme Court overturned a man's conviction for wearing a 'F**k the draft' T-shirt in a courthouse, saying it was protected speech