AO1: Devolution in the UK is a fairly recent phenomenon, only being introduced in 1999 in Scotland and Wales and Northern AO2: Ireland after referendums in the regions, whereas federalism is one of the founding principles of the US system of government AO1: This means that the principles behind devolution are more flexible and more easily amended, as was the case after the 2014 Scottish independence referendum when an increase in power was promised to the Scottish Parliament after a close result in favour of unity. Federalism, however, is a more permanent feature of the US system of government. AO2: The UK Constitution is not a formally entrenched one, which means that devolution was passed by an Act of Parliament, unlike federalism in the US which is entrenched in the US Constitution AO1: This means that devolution can, in theory, be revoked, or can be expanded with additional powers or further devolution being granted. For example, with the expansion of devolution with the introduction of mayors in London and Manchester. AO2: Whereas historically in US federalism, the balance of power between the states and federal government has fluctuated with the actions/laws of President/Congress and the interpretation of the constitution by the Supreme Court. It is also highly unlikely that secession of states in the US would be granted or sought by individual states. AO1: Devolution bodies have a fusion of powers whereas federalism enshrines separation of powers in the state governments AO2: The devolved bodies have executives that are drawn from the legislative bodies, whereas both the states and the federal government elect executives separately from the legislature AO1: Legal sovereignty in the UK still remains with the central government unlike in the US where legal sovereignty is considered to be shared between the state and federal governments AO2: This means that the UK central government is still ultimately able to revoke the powers of the devolved bodies and make decisions on their behalf e.g. on Brexit, whereas the state and the federal governments have powers explicitly granted or reserved to them by the US Constitution AO1: Federalism in the US is equal amongst the states whereas devolution is asymmetric in the UK AO2: This means that the individual states in the US have equal powers to make legislation or to try to influence national legislation, whereas the experience of devolution in the UK depends on the region you live in. For example, the Scottish AO1: Parliament was originally given limited tax powers whereas the Welsh Assembly was not