Current limit using MOSFET
A 30A, 2 milli ohm resistor sounds like a challenge to me, but OK, my daily work is in the micro-Amps range :-).

Since you probably don't need high accuracy, how about using the MOSFET's Rds_on resistance for measuring the current ? Look in the datasheet what Vds will be at 30 A and the Vgs you're going to use. For example at 25 degrees, Vgs = 6 V, Id = 30 A Vds will be around 250 mV.

Use a comparator to compare Vds to a reference voltage of for example 400 mV. When Vds > 400 mV switch off the MOSFET. As you switch OFF the MOSFET Vds will increase to 24 V so the comparator will keep the MOSFET off.