YES

(format LCTRS :logic QF_LIA)
(fun fact 1 :sort (Int Int))

(rule (fact x_0) 1 :guard (<= x_0 0) :vars ((x_0 Int)))
(rule (fact x_1) (* (fact (- x_1 1)) x_1) :guard (>= (- x_1 1) 0) :vars ((x_1 Int)))

Confluent by Parallel Closedness with proof:
no critical pairs

Elapsed Time:   9.95 ms