5. In case of internal disturbance, or when danger threatens from another Canton, the authorities of the Canton threatened shall immediately notify the Federal Council, in order that it may take the necessary measures within the limits of its power, or may summon the Federal Assembly. In urgent cases the authorities of the Canton notifying the federal government of its action, may ask the aid of other Cantons, to which the latter are bound to respond. If the cantonal government is unable to call for aid, the federal authority, having the power, may, and if the safety of Switzerland is endangered shall, intervene without requisition. In case of federal intervention, the federal authorities shall take care that the provisions of the constitution guaranteeing the sovereignty of the Cantons be observed. The expenses shall be borne by the Canton asking the aid or occasioning federal intervention, except when the Federal Assembly otherwise decides on account of special circumstances. 6. In the cases mentioned (Sections 4 and 5), every Canton is bound to afford undisturbed passage for the troops. The troops shall immediately be placed under federal command. 7. The Cantons may require proofs of competency from those who desire to practise the liberal professions; federal legislation may provide for certificates of competency valid for the whole Confederation. 8. Cantons, under the supervision of the Confederation, shall enforce the federal laws relating to weights and measures. 9. Every citizen of a Canton is a Swiss citizen. As such (after furnishing evidence of his right to vote) he can take part at his place of residence in all federal elections and votes. No one shall exercise political rights in more than one Canton. Every Swiss citizen shall enjoy where he is domiciled all the rights of the citizens of the Canton, as also all the rights of the citizens of the Commune. He shall, however, have no share in the common property of the citizens or of the corporation; nor shall he exercise the right to vote in matters pertaining purely to such affairs unless the Canton by legislation has otherwise provided. In cantonal and communal affairs he gains the right to vote after a residence of three months. The cantonal laws relating to the right of Swiss citizens to settle outside the Cantons in which they were born, and to vote on communal questions, are subject to the approval of the Federal Council. 10. No Canton shall expel from its territory one of its own citizens, nor deprive him of his rights, whether acquired by birth or settlement (_origine ou cité_).