If they were served a garnishment order, they are bound to comply with that order. If they failed to comply with the order, they could be liable for damages they caused in failing to comply.
If you are SEVERELY delinquent in your child support obligations, you may have 65% garnished from your wages because child support is protected under a much higher standard than other outstanding judgments/orders. Typically garnishments are 25%; however, when it comes to child support it be between 50 and 65% depeding on the level of delinquency.
Please contact an attorney in order to see if you can reduce your child support obligation. My office number is 702-800-6525.
You cannot sue your employer, as your employer was simply following a court order served on them. For your withholding to be that high, you likely owed arrears and likely a high amount. You should be having your child support reviewed and possibly modified, especially if your income has changed by more than 20% since the last child support order was issued.
Responses are for general information purposes only, and are based on the extremely limited facts given. A consultation with an attorney experienced in the area of law(s) indicated in the question is highly recommended. Information and advice given here should not be relied upon for any final action or decision, as the information is limited by its nature to the question asked and the fact(s) presented in that question. THIS RESPONSE DOES NOT CREATE AN ATTORNEY/CLIENT RELATIONSHIP, particularly considering that the names of the parties are unknown.