Your only constraints might be that they have to include some concepts they learned in class and they must address a present-day issue that somehow relates to the U.S. Constitution. Map out the time frame for the project. If you have older students, you may want the project to last the entire term. If you have younger students, you may limit the project to a week or a month. Try to write down several dates throughout the project where particular project goals must be complete.
Students can also plan their own deadlines.
Generate the driving question and plan the activities that will make up the project. You may need to sketch out activities for your students. Or, you may elect to have students generate a driving question and design all of the activities and present them to you or the class for approval before they proceed. Consider the audience and who would be most interested in the presentation. Discuss inviting other students in the school, parents, people interested in the subject matter, or adults in the community.