Can't encode an array of Strings in Swift

I can't seem to get my arrays to be accepted by my encode function. The error I am getting is

"Cannot invoke 'encode' with an argument list of type '([String], forKey: [String])'

var billID: [String]=[]
var billNumber: [String]=[]
var billTitle: [String]=[]
var billDescription: [String]=[]
var lastAction: [String]=[]
var lastActionDate: [String]=[]

struct stateLawData {
    static let state: String="state"
    static let lastUpdate: String="lastUpdate"
    static var billIDs: [String]=[]
    static let billNumbers: [String]=[]
    static let billDescriptions: [String]=[]
    static let billTitles: [String]=[]
    static let lastActions: [String]=[]
    static let lastActionDate: [String]=[]
}

override func encode(with aCoder: NSCoder) {
    aCoder.encode(stateAbbr, forKey: stateLawData.state)
    aCoder.encode(lastUpdateTime, forKey: stateLawData.lastUpdate)
    aCoder.encode(billID, forKey: stateLawData.billIDs)
    aCoder.encode(billNumber, forKey: stateLawData.billNumbers)
    aCoder.encode(billTitle, forKey: stateLawData.billTitles)
    aCoder.encode(billDescription, forKey: stateLawData.billDescriptions)
    aCoder.encode(lastAction, forKey: stateLawData.lastActions)
    aCoder.encode(lastActionDate, forKey: stateLawData.lastActionDate)
}

This is within a UITableViewController