Two graduate students and a professor on Monday challenged the constitutionality of a 2023 state law that restricts employment of people from China and six other nations at Florida public universities and colleges. Attorneys for Florida International University doctoral students Zhipeng Yin and Zhen Guo and University of Florida professor Zhengfei Guan — all of whom are from China — filed a lawsuit in federal court in Miami. The challenge alleges, in part, that the law is unconstitutional because it is trumped by federal immigration laws. The lawsuit said that under the measure (SB 846), peopl…