Complex sentence: In federal systems, by contrast, sub-unit government is guaranteed in the constitution, so the powers of the sub-units cannot be withdrawn unilaterally by the central government (i.e. without the consent of the sub-units being granted through the process of constitutional amendment).
Split into simpler sentences: In federal systems, by contrast, sub-unit government is guaranteed in the constitution. The powers of the sub-units cannot be withdrawn unilaterally by the central government (i.e. without the consent of the sub-units being granted through the process of constitutional amendment).