What is the ruling on my uncle taking a portion of water to irrigate the family-owned garden in an illegitimate manner, due to the diminishing share of water allocated to the garden by the municipality, and the corruption of irrigation officials who sell water without just cause?

It is not permissible for a Muslim to deceive regarding public or private property through fraud, theft, and betrayal. Administrative corruption does not legalize public funds.

If water becomes so scarce that it no longer suffices to irrigate all orchards, then citizens must be equal in what remains, and anyone taking more than their right is considered to be cheating and stealing.

However, if the water is sufficient for irrigation, but the municipality restricts citizens without legitimate justification, then whoever is able to obtain their right may do so, provided they are secure from fitna (strife) and harm.